Use any herbs or essential oils you fancy. Cinnamon is cool, both as a dried herb and as an EO, in tooth powder.
If you like the taste of anise you might appreciate aniseed, or fennel seed, or eucalyptus EO, or various other anisy herbs and/or EOs. I like thyme and parsley, so I use those.

Using tooth powdersSprinkle some of it onto your wet toothbrush and brush away. When first making these I tried dipping the toothbrush into a jar of tooth powder -- this gets messy and un-powdery very fast.